Semaphorin4F interacts with the synapse-associated protein SAP90/PSD-95

Semaphorins are a family of secreted and membrane-associated proteins invol ved in growth cone guidance during development. Here, we describe the inter action of Semaphorin4F (Sema4F) with the post-synaptic density protein SAP9 0/ PSD-95. Using the yeast two-hybrid system and coprecipitation assays we were able to show an interaction between the extreme C-terminus of Sema4F a nd the PDZ domains of SAP90/PSD-95. Heterologous coexpression of a chimeric EphrinB1/Semaphorin4F protein with SAP90/PSD-95 in COS cells leads to tran slocation of SAP90/PSD-95 from the cytosol to the membrane. Deletion analys is shows that this translocation activity of Sema4F is completely dependent on the presence of the last three C-terminal amino acids. In addition, Sem a4F immunoreactivity is present in synaptosome fractions and enriched in po st-synaptic density fractions. Consistently, in cultured hippocampal neuron s, we demonstrate punctate colocalization of Sema4F and SAP90/PSD-95 in den drites, furthermore we found colocalization of Sema4F with synapsin1 sugges ting a synaptic localization, Our data implicate a new functional context f or semaphorins at glutamatergic synapses.